The history of animal or human motion studies dates back to the 19th century and the use of video cameras. After over one hundred years of development, the optical motion capture system has been widely used in human motion study, especially in medical rehabilitation and sports such as golf, baseball bat swing and pitching. However, the shortcomings of video camera-based motion capture systems are still obvious in the study of sports motion, which features high speed, short duration and path.
Even a high speed camera (up to 250 FPS from OptiTrack) cannot provide a high enough sampling rate to grasp details of human segment motion while pitching a baseball, and to establish the complete 3D motion trajectory, a camera network needs to be set up, limiting the method mainly to laboratory environments. In addition, the analysis required of images after capture results in additional expense, not to mention unwanted delay in the use of the information. The benefit of video analysis is that it provides position information directly from the images. Inertial measurement units (IMUs), on the other hand, require sophisticated manipulation of the acceleration and velocity data to acquire position information.